Whale watching in Bangkok

Bryde's whale

Bryde's whale or the Bryde's whale complex (/bruːdə/brew-də) putatively comprises two species of rorqual and maybe three. The "complex" means the number and classification remains unclear because of a lack of definitive information and research. The common Bryde's whale (Balaenoptera brydei, Olsen, 1913) is a larger form that occurs worldwide in warm temperate and tropical waters, and the Sittang or Eden's whale (B. edeni, Anderson, 1879) is a smaller form that may be restricted to the Indo-Pacific.

Also, a smaller, coastal form of B. brydei is found off southern Africa, and perhaps another form in the Indo-Pacific differs in skull morphology, tentatively referred to as the Indo-Pacific Bryde's whale. The recently described Omura's whale (B. omurai, Wada et al. 2003), was formerly considered a "pygmy" form of Bryde's, but is now recognized as a distinct species.

B. brydei gets its specific and common name from Johan Bryde, Norwegian consul to South Africa who helped establish the first modern whaling station in the country, while B. edeni gets its specific and common name from Sir Ashley Eden, former High Commissioner of Burma (Myanmar). Sittang whale refers to the type locality of the species. In Thailand, locals distinguished Sittang whales different from B.edeni, and it is unclear whether Sittang whales were applied for later classified Omura's whales by locals.

Members of the Bryde's whale complex are moderately sized rorquals, falling behind sei whales, but being larger than Omura's whale and the relatively small minke whales. The largest measured by Olsen (1913) was a 14.95 m female caught off Durban in November 1912, while the longest of each sex measured by Best (1977) at the Donkergat whaling station in Saldanha Bay, South Africa, were a 15.51 m female caught in October 1962 and a 14.56 m male caught in April 1963; both were the offshore form.

At physical maturity, the coastal form off South Africa averages 13.1 m for males and 13.7 m for females, while the South Africa offshore form averages 13.7 and 14.4 m. The coastal form near Japan is slightly smaller, with adult males averaging 12.9 m and adult females 13.3 m.

At sexual maturity, males average 11.9 m and females 12 m near Japan. Sexual maturity is reached at 8–11 years for both sexes in the offshore form off South Africa. At birth, they are 3.95–4.15 m. The body mass of Bryde's whales can range 12–25 metric tons.

Bryde's whale range

Bryde's whale is a baleen whale, more specifically a rorqual belonging to the same group as blue whales and humpback whales. It has twin blowholes with a low splashguard to the front. Like other rorquals, it has no teeth, but has two rows of baleen plates.

Bryde's whales closely resemble their close relative the sei whale. They are remarkably elongated (even more so than fin whales), with the greatest height of the body being one-seventh their total length – compared to 1/6.5 to 1/6.75 in fin whales and only 1/5.5 in sei whales. Bryde's are dark smoky grey dorsally and usually white ventrally, whereas sei whales are often a galvanized blue-grey dorsally and have a variably sized white patch on the throat, a posteriorly oriented white anchor-shaped marking between the pectoral fins, and are blue-grey beyond the anus – although Bryde's off South Africa can have a similar irregular white patch on the throat.

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Bryde's have a straight rostrum with three longitudinal ridges that extend from the blowholes, where the auxiliary ridges begin as depressions, to the tip of the rostrum. The sei whale, like other rorquals, has a single median ridge, as well as a slightly arched rostrum, which is accentuated at the tip. Bryde's usually have dark grey lower jaws, whereas sei whales are lighter grey. Bryde's have 250–370 pairs of short, slate grey baleen plates with long, coarse, lighter grey or white bristles that are 40 cm long by 20 cm wide, while sei whales have longer, black or dark grey baleen plates with short, curling, wool-like bristles.

The 40 to 70 ventral pleats extend to or past the umbilicus, occupying about 58% and 57% of the total length, respectively; sei whales, though, have ventral pleats that extend only halfway between the pectoral fins and umbilicus, occupying only 45-47% of the total body length, whereas their umbilicus is usually 52% of the total body length. Both species are often covered with white or pink oval scars caused by bites from cookie-cutter sharks.

Bryde's whales have an upright, falcate dorsal fin that is up to 46.25 cm in height, averages 34.4 cm, and is usually between 30 and 37.5 cm. It is often frayed or ragged along its rear margin and located about two-thirds of the way along the back. The broad, centrally notched tail flukes rarely break the surface. The flippers are small and slender.

Their blow is columnar or bushy, about 3.0–4.0 m high. Sometimes, they blow or exhale while under water. Bryde's whales display seemingly erratic behaviour compared to other baleens, because they surface at irregular intervals and can change directions for unknown reasons.

They usually appear individually or in pairs, and occasionally in loose aggregations up to 20 animals around feeding areas. They are more active on water surface than sei whales, and this tendency becomes even stronger in coastal form.

They regularly dive for about 5–15 minutes (maximum of 20 minutes) after four to seven blows. Bryde's whales are capable of reaching depths down to 300 m. When submerging, these whales do not display their flukes. Bryde's whales commonly swim at 1.6–6.4 km/h, but can reach 19–24 km/h. They sometimes generate short (0.4 seconds) powerful, low frequency vocalizations that resemble a human moan.

From Wikipedia, the free encyclopedia